Nowadays, the handles of vehicle doors are equipped with devices for detecting the presence of a user. The detection of the presence of a user coupled with the recognition of a “hands free” electronic badge for remote control of access carried by this user, allows remote locking and unlocking of the doors of the vehicle. Thus when the user, carrying the corresponding electronic badge and identified by the vehicle, approaches the handle or touches the door handle of his vehicle, the doors of the vehicle are automatically unlocked. By approaching or by pressing on a precise location of the door handle of the vehicle, called the “unlocking zone”, the door opens without the necessity to unlock it manually. Conversely, when the user, still carrying the necessary badge and identified by the vehicle, desires to lock his vehicle, he closes the door of his vehicle and he approaches or presses momentarily on another precise location of the handle, called the “locking zone”. This action by the user makes it possible to automatically lock the doors of the vehicle.
These presence detection devices generally comprise two capacitive sensors, in the form of two electrodes connected electrically to a printed circuit and integrated into the handle, each in a precise locking or unlocking zone. Generally, one electrode is dedicated to each zone, that is to say one electrode is dedicated to the detection of the approach and/or of the contact of the user's hand in the locking zone and one electrode is dedicated to the detection of the approach and/or the contact of the user's hand in the unlocking zone. One electrode, when it is energized, emits an electric field which defines a detection zone (locking or unlocking zone). The approach of the hand of a user in this detection zone disturbs this electric field and impacts the capacitance seen by said electrode. The measurement of the variation of this capacitance therefore allows the detection of the approach of the user's hand in said zone, in this instance toward the handle. Once this detection has been carried out, it is followed by the dispatching by the capacitive sensor of an unlocking/locking command to the door's unlocking/locking system.
The two zones, locking and unlocking, being situated at distinct locations on the handle, it is necessary that the electric fields emitted by their respective electrodes do not overlap. With this aim, it is known to place a conducting element (for example a copper foil) connected to the electrical ground on the side of the electrode where detection is not desired. This conducting element connected to the ground attracts the electric field emitted by the electrode, and carries out a shielding function in relation to the electric field emitted by said electrode on the side where it is situated.
The space being restricted in a vehicle door handle, it is known to integrate the conducting element and the two electrodes, respectively on each of the two faces of the printed circuit.
With a purely explanatory aim, just a single electrode will be considered, the electrode dedicated to the unlocking zone. A device of the prior art is described with regard to FIGS. 1a, 1b. 
In FIG. 1a is represented a door handle 10 of an automotive vehicle (vehicle not represented) in which there is a device D for detecting presence of a user. Said handle 10 comprises a first exterior surface S1 directed toward the door (not represented) and a second exterior surface S2, opposite the first surface and therefore directed to the opposite side, away from the vehicle, more precisely toward the user (not represented). This detection device D comprises an electrode 12 a face of which is situated in proximity to the first exterior surface S1, control means 13 and a conducting element 11 a face of which is situated in proximity to the second exterior surface S2. The electrode 12 and the conducting element 11 are connected to the control means 13. The control means 13 measure the capacitance seen by the electrode 12 in order to detect the presence of a user. The conducting element 11 is connected to the ground by the control means 13 and carries out a shielding function. These control means 13 are for example a printed circuit comprising a microcontroller (not represented). This detection device D defines a detection zone A (which, in the example illustrated in FIG. 1a, is the unlocking zone) situated between the first exterior surface S1 and the door of the vehicle and whose dimensions are estimated in a frame of reference formed by three perpendicular axes X, Y, Z. In the subsequent description, we will consider solely the unlocking electrode 12 dedicated to the unlocking zone A, although the invention can also be applied to the electrode dedicated to the locking zone (not represented). As illustrated in FIG. 1a, we will consider the unlocking zone A to be a zone situated between the handle 10 and the vehicle.
This unlocking zone A is also called “sensitivity” of the detection device D.
This prior art detection device D is known to the person skilled in the art.
There exist various types of door handles 10. As represented in FIG. 1a, certain handles 10 have their second exterior surface S2, covered with a layer of paint P, for example of identical color to that used for the body shell of the vehicle, that is to say with a coating of plastic type. Other handles 10 have their second exterior surface S2 covered, with a purely esthetic aim, with a metallic coating 20, for example covered with a metal comprising chromium (cf. FIG. 1b).
However, the presence of this metallic coating 20 on the second exterior surface S2 disturbs the electric field emitted by the unlocking electrode 12. Indeed, this metallic coating 20 is connected to the electrical ground by way of the vehicle (which is itself electrically grounded), and is conducting. It attracts the electric field of the electrode 12 toward itself and acts as a second shielding element (the first shielding element being the conducting element 11). This is illustrated in FIG. 1b. In the presence of the metallic coating 20 on the second exterior surface S2, the dimensions (in the X, Y, Z frame of reference) of the new unlocking zone A′ are markedly smaller than that of the locking zone A obtained with a handle whose second exterior surface S2 is covered with a layer of nonmetallic paint P.
Thus, this metallic coating 20 markedly reduces the dimensions of the unlocking zone A′. The consequence of this is to create a delay in the detection of the presence of the user's hand in the unlocking zone and therefore a delay in the unlocking of the door. In certain cases, this disturbance is such that detection of the presence of the user is then no longer possible. It will be understood that this is not desirable for the user who expects fast unlocking of the doors of his vehicle.
A possible solution to this problem is to increase the range of the electric field emitted by the electrode, by increasing its sensitivity. This solution has, however, the major drawback of increasing the electrical consumption of the detection device, this not being desired, the device operating mainly when the car is stopped and being powered by the battery of the vehicle. A second drawback of this solution is the obligation to have two different detection devices, one for each type of handle coating. However, this diversity of detection devices gives rise to additional costs during the development and production of these detection devices.